EP2814704A1

EP2814704A1 - Method for determining an emergency braking situation of a vehicle

Info

Publication number: EP2814704A1
Application number: EP13704350.1A
Authority: EP
Inventors: Karsten Breuer; Dirk Sandkühler
Original assignee: Wabco GmbH
Current assignee: ZF CV Systems Hannover GmbH
Priority date: 2012-02-14
Filing date: 2013-02-01
Publication date: 2014-12-24
Anticipated expiration: 2033-02-01
Also published as: JP2015508726A; EP2814704B1; PL2814704T3; WO2013064705A1; JP6195578B2; ES2596277T3; CA2860892C; CN104114423A; PL2814704T5; CN104114423B; KR101661047B1; ES2596277T5; KR20140129115A; EP2814704B2; US20150012204A1; CA2860892A1; US9566959B2; RU2014137111A; RU2624974C2; DE102012002695B4

Abstract

The invention relates to a method for determining an emergency braking situation of a vehicle (1), in which the vehicle (1) determines at least the following state variables: its own velocity (vi), its own longitudinal acceleration (a1), its relative distance (dx) from an object (2) in front, and a second speed (v2) and second acceleration (a2) of the object (2) in front, wherein by means of an evaluation method it is determined from the state variables (vi, a1, dx, v2, a2) whether an emergency braking situation is present. According to the invention there is provision that various evaluation methods are used as a function of the state variables (vi, a1, dx, v2, a2) to assess whether an emergency braking situation is present, wherein as a function of the state variables it is determined which of the plurality of evaluation methods is used, wherein the various evaluation methods comprise at least the following evaluation methods: a movement equation evaluation method in which a movement equation system of the vehicle (1) and of the object (2) in front is determined, and a second evaluation method in which a braking distance of the vehicle (1) is determined.

Description

Method for determining an emergency braking situation of a vehicle

The invention relates to a method for determining an emergency braking situation of a vehicle, a control device for carrying out such a method and a driving dynamics control system with such a control device.

In particular, the invention relates to a method for assessing the risk of a rear impact when driving on a road, on which a preceding object, in particular a vehicle, is located.

For this purpose, it is generally known to set up equations of motion in order to determine a collision time in the current driving behavior of one's own vehicle and of the previous vehicle. Furthermore, it is also generally known to determine desired delays in order to avoid possible collisions.

EP 1 539 523 B1 or DE10258617B4 describes a method and a device for triggering an automatic emergency braking operation of a vehicle. Here, the own speed and the own acceleration of the vehicle are determined and a minimum distance is set as the target safety distance. Furthermore, a target relative speed between the two vehicles is set, which is to be achieved with the completion of the automatic emergency braking operation. In addition, the determined currently existing relative acceleration between the two vehicles is used.

DE 10 2006 019 848 B4 describes a device for reducing the effects of a vehicle collision, in which an obstacle with its relative distance and its relative speed detected and a possible collision or accident is assessed, whereupon optionally an occupant protection means can be activated. Such systems are also known as pre-crash systems.

JP 2004038245 A1 shows an obstacle detector for vehicles in which additionally a detected steering wheel actuation is used. EP 0 891 903 B1 describes an automatic emergency braking function in which the possibility of bypassing the obstacle is also assessed. EP 1 625 979 B1 describes a method and a device for triggering emergency braking, in which a collision probability and furthermore a risk to one's own vehicle in the event of an emergency brake release are determined and the triggering threshold for the emergency braking can be changed as a function of this determined hazard. EP 1 803 109 B1 describes a method for determining relevant objects in the vicinity of a vehicle, in which collision-relevant values from vehicle and / or environmental sensor data are calculated taking into account possible avoidance maneuvers or braking processes.

A disadvantage of such conventional methods is generally that they are often limited only to specific driving situations and thus do not always contribute in time to accident prevention of autonomous braking. Furthermore, the triggering of emergency braking may possibly also occur too early and thus possibly unnecessarily.

Furthermore, various spacer systems are known without emergency braking. The Bendix-Wingman Adaptive Cruise ACB Adaptive Cruise System incorporates a distance system to keep the distance to a preceding vehicle constant. In this case, warning display signals and also emergency braking signals can be output for the automatic execution of an emergency braking method. For this purpose, the distance to the preceding vehicle is measured, for example, with radar. The invention has for its object to provide a method, a corresponding control device for its implementation and a vehicle dynamics control system that allow safe detection of an emergency braking situation and keep the probability of unauthorized emergency braking low.

This object is achieved by a method according to claim 1 and a control device according to claim 15. The dependent claims describe preferred developments. In this case, a driving dynamics control system is additionally provided with such a control device or for carrying out the method.

According to the invention, different evaluation methods are thus used in order to use a suitable evaluation method depending on the currently present driving situation.

According to a first evaluation method, which represents a motion equation evaluation method, equations of motion of both the own vehicle and the object in front of the vehicle are set up and evaluated depending on whether an emergency braking situation exists. Depending on this evaluation, in particular a demand delay can be calculated below. The equations of motion can be set up in particular in the second order of the time, ie with initial value, linear term and quadratic term, so that a common equation system or a common equation of motion of the own vehicle and front object can be formed, from which a subsequent undershooting of a minimum distance and / or a collision can be determined. In contrast, according to a second evaluation method, a braking distance analysis is carried out in which the braking distance of at least one's own vehicle can be determined and evaluated.

The invention is based on the idea that in a typical driving situation of one's own vehicle behind a preceding vehicle, an emergency braking situation can be determined by equations of motion of the driver's vehicle and of the vehicle's front object. In particular, for such a motion equation evaluation method, second-order equations of motion may be formed in time, i. with a relative distance as a zero-order term of time, the velocities (or the relative velocity) as first-order terms in time, and the accelerations as second-order terms in time. A system of equations can thus be formed from these equations of motion, with which it is determined whether an approximation to a permissible minimum distance (for example a minimum distance of 1 meter or also zero) will subsequently follow. In this case, reaction times of the brake systems of the vehicle (eg for ventilating the brakes) and / or of the driver can be included in particular, since changes due to active interventions will only have an effect after the reaction time.

According to the invention, it is now recognized that such an approach of a system of equations, in particular also equations of motion in the second order of time, can lead to misjudgments in some situations. Equations of motion of second order in the time with negative acceleration, ie a deceleration or deceleration of one's own vehicle or of the preceding object, mathematically also include a fictitious reverse drive following a complete standstill of the vehicle or of the object. However, such fictitious reversing is physically nonsensical, since a deceleration of a vehicle by braking intervention or engine-retarder intervention (or even, for example, air friction) Although it can lead to a deceleration (negative acceleration) of a positive speed to a standstill, however, no acceleration of a stationary vehicle will cause more to the rear. At standstill of the vehicle, the physically acting braking effect, ie the negative acceleration, rather drops to zero, ie the vehicle comes to a standstill, but does not start a reverse drive.

Thus, in the mathematical equation system fictitious, but nonsensical collisions can occur which occur during a reverse drive, in particular in a fictitious reverse drive of the preceding vehicle in front.

Therefore, according to the invention, the equation of motion evaluation method is only used if it is considered useful. Advantageously, criteria for determining different situations are used to select the appropriate rating method.

If it is determined that the first evaluation method, ie the motion equation evaluation method, does not make sense, another evaluation method is used according to the invention, whereby at least one second evaluation method, preferably a braking distance evaluation method with a braking distance analysis, is provided. Here, a braking distance of the own vehicle is preferably determined and evaluated without the inclusion of the exact equations of motion of the own vehicle and the front object. Preferably, a time-dependent admissibility criterion is defined, which compares the intrinsic deceleration time of the first, own vehicle with the object deceleration time of the front, second object, which represents a particularly simple determination and determination of the admissibility of the first or second evaluation method. In this case, the self-braking time can be up to the achievement determine the minimum distance while simultaneously reducing the relative speed of the own, first vehicle to the front, second object. The object deceleration time is the time it takes the front, second object to standstill.

According to the invention, an upstream criterion can also be used in advance, whether the relative distance after the reaction time does not already reach or falls below the minimum distance, and thus an emergency braking situation already exists; this can be considered as an upstream ("zeroth") assessment procedure, so that the first and second assessment procedures do not even become relevant.

The own first acceleration can be measured by a longitudinal acceleration sensor and / or determined by temporal derivation of the own, first speed. The relative distance to the front object can be determined in particular by a distance sensor. From this, therefore, the second speed of the object can be determined at least from the temporal behavior of the signal of the relative distance and its second acceleration as the time derivative thereof.

In principle, however, the second speed of the object may also be e.g. be detected by a Radardoppler measurement. The evaluation of the emergency braking situation according to the invention can then be determined in particular by determining the demand delay of the own vehicle.

In a path-time diagram, the equations of motion of the second order of time thus result in parabolas; in a negative acceleration, ie deceleration or deceleration, the parabolas are open at the bottom. The corresponding speed curves form straight lines, with a deceleration thus with negative slope. The falling branches of a parabolic movement curve in the path-time diagram and correspondingly negative values in the velocity-time diagram are evaluated according to the invention as physically nonsensical; Such conditions, which lead to a wrong evaluation, are excluded according to the invention by means of suitable criteria.

Thus, the fictitious case can be excluded that the front vehicle at a negative acceleration, i. Delay or braking, in a subsequent fictitious backward movement after its stoppage triggers a collision with the own vehicle.

In order to exclude this case of fictitious, collision-causative reversing, it is advantageously checked which times or which braking paths the object and the own vehicle need to standstill. If the own vehicle reaches standstill sooner or simultaneously with the front object, according to a preferred embodiment, advantageously the first evaluation method can be applied. However, if the own vehicle reaches standstill later than the front object, the equation of motion evaluation method is advantageously not used, since a fictitious collision case is determined on subsequent reversing of the front object. This results in a criterion of admissibility for the equation of motion equation method, whereby the second evaluation method is subsequently used in the event of non-compliance.

The second method of evaluation basically uses the braking distances, but not the dynamics of the vehicles until their standstill, ie their exact equations of motion. Thus, theoretically, the case could arise that while the calculated values at the time of standstill a safety distance between the own vehicle and the front object is maintained, due to the actual chen dynamics of their own vehicle but until then a collision (or shortfall of the minimum distance) has occurred. According to the invention, however, it is recognized that the first and second evaluation methods complement each other ideally. Such collisions can already be detected by the motion equation evaluation method. If, therefore, the admissibility criterion for the motion equation evaluation method is fulfilled and the motion equation evaluation method can be used, collisions until the standstill are reliably detected. If, however, the equation of motion evaluation method can not be used due to non-compliance with the admissibility criterion, then in the second evaluation method, no further false statement can be made to the effect that, at the time of standstill, the safety distance or minimum distance is maintained, but until then a collision occurs. Such collisions would have been recorded in the equations of motion assessment procedure.

Thus, a safe and feasible with relatively little computational effort method is created, which also reliably detects different initial movement states of the own vehicle and the front object. In this case, an unnecessarily early emergency braking with resultant dangers of both the own vehicle and possibly behind it driving vehicles with high security is excluded.

According to the invention, both an automatic emergency braking triggered by the method or a warning indication signal can be issued to the driver. In the case of an exact determination, reaction times can be included, which thus include the apparatus-related times for filling the brakes and actuating the actuators in an automatic emergency brake system and also take into account the reaction time of the driver when a warning indication signal is output to the driver. According to a particularly preferred embodiment, different cases are hierarchically subdivided. A first case can first of all check whether the relative distance between the own vehicle and the front object after the reaction time is smaller than a minimum distance to be maintained; if this first criterion is met, emergency braking is always initiated immediately. Only then will z. For example, consider four cases, each of which determines whether the first or second assessment procedure is to be used. In these cases, advantageously, the acceleration of the front object and the relative speed, in particular the relative speed after the reaction time is used. Thus, a case distinction can be made on the basis of only these two quantities, in particular in four or five different cases.

In these cases, then, if necessary, the motion equation evaluation method may first be checked, and if this is not the case then the second evaluation method is used. In two other cases, e.g. only the equations of motion evaluation method or the second evaluation method are used. Furthermore, there may be a case in which the acceleration of the front object is positive and also the differential or relative speed is positive, so that it can be recognized that altogether there is no danger of collision.

The control device according to the invention can in particular cut off the engine torque depending on the result of the method according to the invention, for which purpose it can be used, for example. B. outputs control signals to an engine control unit.

The invention will be explained below with reference to the accompanying drawings of some embodiments. Show it: Figure 1 shows the representation of a street scene with two vehicles driving one behind the other.

Fig. 2 to 7 diagrams of the distances and speeds of the two vehicles and their relative distance according to different initial conditions.

A first, own vehicle 1 drives behind a front object 2, in this case a second, front vehicle 2, on a roadway 3. In the following, only movements in the common vehicle longitudinal direction are considered. The first own vehicle 1 is at a position x1 and travels at a speed vi and an acceleration a1. A braking process thus represents an acceleration a1 with a negative value. Accordingly, the second, front vehicle 2 is at a position x2, runs at a second speed v2 and a second acceleration a2. All quantities x1, vi, a1; x2, v2, a2 are time dependent. There are subsequently equations of motion of the second order of time for the two vehicles, the first, own vehicle 1 and the front vehicle 2, set up. In this case, preferably a constant first, own and second acceleration a1, a2 is assumed, at least until initiation of a braking process of the own vehicle 1.

The own vehicle 1 has a distance sensor 4 for determining a relative distance dx between the first, own vehicle 1 and the front vehicle 2, a vehicle dynamics system 5 with a control device 6, a speed sensor 7 and the vehicle 6 controllable vehicle brakes 8. The distance sensor 4 outputs a relative distance measuring signal M1, and the speed sensor 7 outputs a speed measuring signal M2 to the control device 6. In this case, the speed sensor 7 can also be provided by the ABS wheel speed sensors be formed. Furthermore, the control device 6 outputs brake control signals M3 to the vehicle brakes 8.

In accordance with various criteria, a case distinction is made in different scenarios, in which different evaluation methods or evaluation methods are then used to determine whether a collision can occur and when, if necessary, emergency braking should be initiated.

All calculations take place in the rear first, own vehicle 1, which thus determines the danger of a collision collision (rear collision) with the front vehicle 2. Depending on the determination, either an emergency braking by an autonomous emergency braking system (AEBS) of the first, own vehicle 1 can be initiated automatically and / or a warning indication signal Sil can be sent to the driver of the first vehicle via a warning display 9 Vehicle 1 are issued.

For these two cases, a different reaction time t1 can be used. In the case of an automatic AEBS, a shorter reaction time t1 must be used, which is essentially determined by the time required to build up brake pressure in the brakes (brake ventilation). In a collision warning (forward collision warning, FCW) to the driver is first the reaction time of the driver, z. B. between one second in an attentive driver and two seconds in a distracted or inattentive driver, and in addition to consider the apparatus required time to build up the internal brake pressure.

In the following, evaluation methods for the braking criterion, ie the determination of a time at which the emergency braking is to be initiated, are described. The basic idea here is, if possible, to set up the second-order equations of motion of the first, own vehicle 1 and of the second, front vehicle 2 and to determine from this whether emergency braking should be initiated. Thus, a trajectory or movement parabola is set up, which may possibly lead to a standstill in the case of negative acceleration, but mathematically also describes a backward travel of the respective first own vehicle 1 and / or of the relevant second front vehicle 2 in the subsequent time values. However, since the negative acceleration stops due to the braking effect at standstill of the first own vehicle 1 and the second front vehicle 2 and does not lead to a reverse or further acceleration in the reverse direction (negative direction), a distinction is made according to the invention, if the movement parables or Second order equation of motion of this physically nonsensical case with an incorrectly possibly a collision (or falling below the minimum distance) indicative situation is detected in subsequent fictitious reversing. If this case can be excluded, the equations of motion of second order are set up in time. However, if it is recognized as such or corresponding case, a braking distance observation is performed according to the invention.

1. Evaluation procedure BV1:

Determination of the braking criterion from the equations of motion of the second order.

The position of the second, front vehicle 2 (object) is to be represented as x2 = x2_0 + v2 ^■ t + i a2 · t ² . Equation 1 with x2_0 of position at time t = 0. Accordingly, the position of the own, first vehicle 1 is as follows: x1 = x1_0 + vi * t + ^ a1 ^■ t ² . Equation 2

Here, x1 refers to the front end point of the own, first vehicle 1; however, x2 refers to the posterior endpoint, i. H. the rear of the front, second vehicle 2, so that the relative distance dx is measured directly from the distance sensor 4. At dx = 0 there is thus a collision or rear-end collision.

The relative distance dx can be represented as dx = (x2_0 - x1_0) from Equation 1 and 2 + (v2 - v1) - t + (a2 - a1) · T ^2. It follows that dx = dx_0 + dv * t + ^ * (a2-a1) * t ² , equation 3 with dv = v2-vi, ie the relative velocity and dx_0 = x2_0-x1_0, a relative distance dx_0 determined at time t = 0 ,

This equation thus describes the relative movement between the first, own vehicle 1 and the second, front vehicle 2. In order to avoid a collision between the first own vehicle 1 and the second front vehicle 2 as late as possible, the invention provides: The acceleration a1 of the own vehicle 1 (negative in magnitude) is now determined in order to bring the relative speed dv to zero if at the same time a permissible minimum distance dxjnin is reached, ie dx = dx_min. The idea here is that at a relative speed dv = 0, no approach of the first own vehicle 1 to the second front vehicle 2 takes place, which should have taken place when the minimum distance dxjnin has been reached.

If, therefore, these two conditions dv = 0 and dx = dx_min are used in equation 3, the following value dv ² results as the first setpoint acceleration a1_d_1

a1_d_1 = a2 - Equation 4.

2 (<± _0- <£ t_min)

Herein, the value a1_d_1 is referred to as "first" target acceleration and provided with the suffix "_1", since after the first evaluation process BV1, i. the equation of motion valuation method.

In order to calculate the required first target acceleration a1_d_1 of the own vehicle 1, the relative speed after the reaction time t1 is determined as dv_t1. In this case, it is thus assumed in the above equations that the accelerations a1 and a2 are constant between the time t = 0 and t = t1. This results in dv_t1 = dv + (a2-a1) · t1 equation 5.

In addition, to determine the first desired acceleration a1_d_1, the relative distance dx_t1 is determined after the reaction time t1. In turn, it is assumed that the accelerations a1 and a2 are constant. With the relative distance dx or dx_0 determined by the distance sensor 4 at the time t = 0 can thus be calculated as follows. fl ²

dx_t1 = dx_0 + dv * t1 + (a2-a1) · Equation 6.

Thus, based on dv_t1 and dx_t1, the required first target acceleration a1_d_1 of the own vehicle 1 can be calculated as follows: a1_d_1 = a2 (< ^v - ^f1 ) ² Equation 7.

2 · (dx _ 11 - dx _ min)

This equation 7 is used to calculate the required first target acceleration a1_d_1 in the following example. In this example, the preceding, second front vehicle 2 accelerates with a second acceleration a2 = -3 m / s ² , ie the front, second vehicle 2 brakes from a second initial speed v2 = 60 km / h. The own, first vehicle 1 has an initial speed of v1 = 90 km / h. The minimum distance dx_min is set to 1 m, the relative distance dx_t0 at the time t = 0 between the first own vehicle 1 and the second front vehicle 2 is determined by the distance sensor 4 to dx_0 = 60 m. With a reaction time t1 = 1 s, this example leads by equation 7 to a required first target acceleration of a1_d_1 = -4.3 m / s ² . The following movement curves of the first own vehicle 1 and the second front vehicle 2 are shown in Fig. 2.

The speed curves of the first speed vi and the second speed v2 thus fall linearly and reach the zero line. The path curves x1 and x2 form parabolas open at the bottom, which initially increase to their respective vertex S1 or S2, at which vi and v2 also become 0; the right side of the parabolas becomes According to the invention evaluated as physically nonsensical, since they each corresponds to a fictitious backward movement.

In the example chosen, a standstill of the second front vehicle 2 is reached after t = 5.5 s, i. H. v2 (t = 5.5 s) = 0. Own vehicle 1 reaches standstill vi = 0 at t = 6.8 s.

Thus, in this example, starting at t = 5.5 s, d. H. the fictitious backward movement of the second front vehicle 2, the impermissible area in this diagram.

In this example of Fig. 2, the point where the conditions dv = 0 and dx = dx_min are satisfied is placed at t = 9.7 s when the two straight lines of vi and v2 intersect. However, this fictitious intersection is already in the impermissible range, and even both vehicle speeds are negative with vi = v2 = -44.8 km / h, d. H. each a fictitious backward movement. The result is thus evaluated according to the invention as inadmissible.

A comparison of the vertices S1 and S2, d. H. However, the positions x1 (vi = 0) = 94.8m and x2 (v2 = 0) = 107.1m show that collision would have been avoided with this result for a1_d_1 in this situation. The relative distance dx between the two vehicles 1 and 2 at the time of standstill is 107.1 m - 94.8 m = 12.3 m higher than the assumed minimum value dx_min, from which it follows that the deceleration or acceleration with a1_d_1 too strong was, d. H. represents an excessive braking effect. Thus, an autonomous braking system would be activated too early.

The weakness of this first method or first approach is particularly evident in situations where z. B. initially, ie at t = 0, a large relative distance dx between the first, own vehicle 1 and the second, front vehicle 2 and a high deceleration of the front vehicle 2 are present; In such situations, it is thus faster to the fictitious backward movement of the front vehicle 2 with subsequent fictitious collision in backward movement of the front vehicle 2. In Fig. 3 is a comparison with Figure 2 modified situation is shown; compared to Fig. 2, the velocities v2 = 60 km / h, vi = 90 km / h at time t = 0 and the minimum distance dx_min = 1 m kept constant. However, the front vehicle 2 now accelerates with a2 = -6 m / s ² , ie high deceleration, and the initial relative distance dx_0 between vehicle 1 and 2 is dx_0 = 90 m. In this case, equation 7 leads to a first desired acceleration a1_d_1 of -7.3 m / s ² . The movement curves are shown in FIG.

In this example of FIG. 3, a comparison of the positions of the vehicles at their vertices S1 and S2, d. H. x1 (vi = 0) = 68.9 m and x2 (v2 = 0) = 1 14 m, that the relative distance dx at standstill between them is 45.1 m. The point at which the conditions dv = 0 and dx = dx_min are satisfied again lies in the impermissible range after the second front vehicle 2 has come to a standstill, i. H. at t = 1 1, 8 s, v 2 = -195 km / h, similar to the above example of FIG. 2.

Thus, according to the invention, this approach is based on equations of motion of the second degree of time with the boundary conditions to achieve a relative speed dv = 0 (same speed of the vehicles) with simultaneous setting of a minimum distance dx_min, for such cases not used or rejected.

FIG. 4 shows a further example in which the conditions dv = 0 and dx = dx_min are reached before the front vehicle 2 comes to a standstill. The front vehicle 2 brakes with a2 = -2 m / s ² from an initial second speed of v2 = 50 km / h. Your own driving tool 1 has an initial speed of v1 = 90 km / h. The value for dx_min is set to 1 m, and the initial relative distance dx_0 between the two vehicles 1, 2 is dx_0 = 40 m. The reaction time is again at t1 = 1 s. For this example, equation 7 leads to a value a1_d_1 of -5.2 m / s ² . The resulting movements are shown in FIG. The front vehicle 2 comes to a standstill after t = 7 sec. The conditions dv = 0 and dx = dx_min are fulfilled at t = 5.1 s. In this situation, the result represents a time that is within the allowed range; equations 3 and 4 represent realistic motions of both vehicles 1, 2 with vi, v2> 0. Thus, the value a1_d_1 calculated on the basis of equation 7, in this situation of figure 4, represents an allowable value to be evaluated the situation can be used.

Thus, according to the invention, it can be stated that equation 7 delivers permissible values as long as both vehicles 1, 2 are still driving, ie. H. have not yet come to a standstill. By contrast, the results become inadmissible when one of the vehicles 1, 2 comes to a standstill.

In the graphic representation of the figures, an impermissible range thus begins when the paraboloidal path curve x1 or x2 of one of the vehicles 1, 2 reaches its vertex S1 or S2; Correspondingly, the velocity lines then intersect the zero point and the zero axis, respectively.

Therefore, according to the invention, an admissibility criterion Zk1 is set in order to check the admissibility of this first evaluation method. For this purpose, the intrinsic deceleration time t1_dv, which requires the own vehicle 1 up to the conditions dv = 0 and dx = dx_min, is compared with the object deceleration time t2_stop which the second front vehicle 2 requires for deceleration to standstill. If the admissibility criterion Zk1: t1_dv <t2_stop is satisfied, it is ensured that the situation according to Figure 4 is to be assessed, ie the own vehicle 1 reaches dv = 0 and dx = dx_min, before the front vehicle 2 comes to a standstill. Thus, a permissible result is indicated, ie the motion equation evaluation method (first evaluation method) is permissible.

The object deceleration time t2_stop is calculated based on its current second speed v2 and second acceleration a2:

(0km / h - v2) v2 ~, ·.

t2 stop = - - = Equation 8

^~ 22 22

The own deceleration time t1_dv required by the own vehicle 1 is based on the result for a1_d_1 of equation 7 and can be calculated as ung 9

This results in the following evaluation criteria for admissibility or validity:

If the admissibility criterion Zk1 is satisfied, i. t1_dv <t2_stop, then the first target acceleration a1_d_1 is valid, i. the equation of motion evaluation method (first evaluation method) BV1 with Equation 7 is allowed.

If t1_dv> t2_stop, then a1_d_1 is not allowed.

In order to detect these impermissible situations in which the determination described above does not lead to a permissible result to be able to determine and a second, in this case permissible target acceleration or demand delay a1_d_2, the following second evaluation method BV2 or evaluation method is applied:

Second evaluation procedure BV2:

The second evaluation method BV2 calculates the distance that the own vehicle 1 has to standstill behind the front vehicle 2 available.

On the basis of this distance, the second target acceleration a1_d_2 is calculated, which is required to standstill within this distance, starting from the current speed vi of the own vehicle 1. All parts that contribute to this calculation are included in this calculation. These parts or sections are:

the current distance dx between the own vehicle 1 and the front vehicle 2,

the distance s2_stop which the front vehicle 2 travels from its current second speed v2 to its standstill during the deceleration process at its current second acceleration a2 (deceleration),

the distance s1_react, which travels the own vehicle 1 during the reaction time t1,

- The minimum distance dx_min, which should remain between the vehicles 1 and 2, after both have come to a standstill.

The maximum braking distance s1_br available for one's own vehicle 1 is calculated in accordance with s \ _br = dx + sl_stop - s \ _ react - dx_min Equation 10, with s2 _ stop - equation 1 1

2 - a2 s \ react = vl / l + - al fl ² Equation 12

2

In order to calculate the required second target acceleration a1_d_2 of the own vehicle 1, the speed v1_t1 of the own vehicle 1 after the reaction time t1 is first determined. This is done on the assumption that the own vehicle 1 drives at a constant acceleration a1 during the reaction time t1: vl_il = vl + al - il equation 13

This equation 13 thus indicates the speed of the own vehicle 1 after the reaction time t1. On the basis of v1_t1 and s1_br, the required acceleration of the own vehicle 1 is determined as a second setpoint acceleration a1_d_2

(yl _rl) ²

a \ d 2 = - Equation 14

2 s _br

The second setpoint acceleration a1_d_2 determined in equation 14 thus represents the demand delay of the second evaluation method BV2 and is used in the following example. The driving situation of this example is similar to Example 1 of Figure 2, to allow a direct comparison of the two approaches for calculating the desired acceleration or demand delay. The front vehicle 2 accelerates (brakes) with a2 = -3 m / s ² from an initial second speed of v2 = 60 km / h. The own vehicle 1 has an initial speed of v1 = 90 km / h. The value for dx_min is set to 1 m, and the initial relative distance dx_0 between the two vehicles 1 and 2 is dx_0 = 60 m. The reaction time t1 is 1 s. The second evaluation method BV2 according to equation 14 leads to a demand delay (second set acceleration) a1_d_2 of -3.9 m / s ² . By contrast, the equation of motion evaluation method BV1 according to Equation 7 resulted in a value of the first setpoint acceleration of a1_d_1 of -4.3 m / s ² , which, as described above, should be regarded as an invalid result, since Equation 7 reproduces a result, whose time is after the standstill of the first own vehicle 1 and the second front vehicle 2, in which the first own vehicle 1 and the second front vehicle 2 drive backwards. In FIG. 5, these relations are represented by the curves or graphs already known from FIG. 2, and the further curves.

The second evaluation method BV2 thus takes into account only the end points of the situation when the first own vehicle 1 and the second front vehicle 2 have come to a standstill; the deceleration phases are not considered separately for the first own vehicle 1 and the front vehicle 2. The deceleration path s2_stop of the front vehicle 2 is used for the calculation of s1_br. Explicit calculation of this value avoids unwanted consideration of the rearward movement of the front vehicle 2. Thus, in this approach, a standstill of the front, second vehicle 2 is considered after the deceleration process. This is represented by the curve x2 in FIG. It represents this standstill or this fixed position. In FIG. 5, x2 = const and v2 = 0 after the front, second vehicle 2 has come to a standstill. With this method, it becomes possible to calculate a correct target acceleration in such situations in which the own vehicle 1 reaches the standstill after the front vehicle 2 stands still.

Thus, the curves in Figure 5 show that Equation 14 represents the correct value for the target acceleration in this situation, since it represents exactly the acceleration required to collide with to avoid the front vehicle 2 and to stop the first, own vehicle 1 at a distance of 1 m behind the front vehicle

2 to come. Any stronger deceleration would also prevent a collision with the front vehicle 2, but would cause the stall to occur too early, i. at a larger relative distance dx than the desired value of dx_min = 1 m reach. Thus, with an AEBS, this would lead to early activation of the braking system.

The second example of the motion equation evaluation method BV1 shown above shows another situation in which the motion equation evaluation method BV1 leads to an excessively high value for the first target acceleration a1_d_1. These situations are generally characterized by a large relative distance dx between the first own vehicle 1 and the second, front vehicle 2 and a strong deceleration a2 of the front vehicle 2. Referring to FIG.

3 uses an initial second speed v2 = 60 km / h of the front vehicle 2, an initial speed v1 = 90 km / h of the own vehicle 1, a minimum distance dx_min = 1 m, a second acceleration a2 = -6 m / s ^{2 of} the front vehicle 2 and an initial relative distance dx_0 = 90 m. In this example, Equation 7 resulted in a first target acceleration of a1_d_1 of -7.3 m / s ² . By contrast, equation 14 leads to a second setpoint acceleration of a1_d_2 = -3.6 m / s ² in this situation. The resulting motions according to the two delay values are shown in FIG.

The front vehicle 2 reaches a standstill at t = 2.8 s. The value for a1_d_1 according to the motion equation evaluation method BV1 described above is too large and gives a standstill distance of 45.1 m, as stated above. On the other hand, the second evaluation method BV2 leads to a value of the second target acceleration a1_d_2 of -3.6 m / s ² , which corresponds to the minimum delay that is required. to avoid the collision with the front vehicle 2 of this situation. FIG. 6 shows that the own vehicle 1 stops at t = 8 s. and reached a relative distance of 1 m.

In contrast, the example 3 shown above in connection with the equation of motion evaluation method BV1 supplies a correct result for the first setpoint acceleration a1_d_1 with the motion equation evaluation method BV1. In this case, the forward vehicle has decelerated = -2 m / s ² at an initial speed of 50 km / h 2 with a2. The own vehicle 1 has an initial speed of 90 km / h. The value for dx_min is set to 1 m and the initial relative distance dx_0 between the first own vehicle 1 and the second front vehicle 2 is 40 m. In this example, equation 7 results in a first target acceleration of a1_d_1 = -5.2 m / s ² . Equation 14, on the other hand, leads to a result of a1_d_2 = -5.02 m / s ² for this situation. The resulting motions for both acceleration values are shown in FIG.

FIG. 7 shows that the deceleration with the second setpoint acceleration a1_d_2 determined according to the second evaluation method BV2 leads to a standstill of the own vehicle 1 at t = 6 s. The traveled distance of the own vehicle 1 shown as x1 is 1 m smaller than the position x2 of the front vehicle 2 when the front vehicle 2 is at t = 7 s. stationary. But before the own vehicle 1 reaches a standstill with a second set acceleration a1_d_2, the relative distance dx_2 between the own, first vehicle 1 and the front, second vehicle 2 determined by the second evaluation method BV2 becomes smaller than 0. This means that one's own Vehicle 1 collides with the front vehicle 2 before the own vehicle 1 and the front vehicle 2 reach the standstill. Thus, the value of the second evaluation method BV2 for the second setpoint acceleration a1_d_2 in this example is not correct. rect or does not lead to a correct calculation of the deceleration value in order to avoid a collision with the front vehicle 2. Rather, in such a case, the equation of motion evaluation method BV1, ie a1_d_1 according to equation 7, is to be used.

The second evaluation method BV2 therefore only considers the end points of the braking situation when both vehicles 1, 2 have come to a standstill. However, it does not check the crossing points of the trajectories of both vehicles 1, 2 possibly occurring during the deceleration process, i. intermittent collisions.

Thus, according to the invention, both evaluation methods BV1, BV2 are used for a correct calculation of the braking criterion.

For the specific case that the front vehicle 2 is stationary and the own vehicle 1 is approaching, both evaluation methods BV1, BV2 lead to the same result

-dv_t1 = v1J1,

dx_t1 - dx_min = s1_br

a2 = 0

Hereinafter, taking into account the above, different cases for the use of the evaluation methods BV1 and BV2 are distinguished, which depend substantially on the acceleration a2 of the front vehicle 2 and the relative speed between the vehicles 1 and 2 after the reaction time dv_t1 has elapsed.

To test the need for automatic brake control to avoid collision, the following cases are checked: In a first criterion K1, it is checked whether the distance dx_t1 between the vehicles 1 and 2 after the reaction time t1 is smaller than the minimum distance dx_min: dx_t1 <dx_min.

If the first criterion K1 is met, there is a need for an automatic braking, since the driver is not able to automatically initiate a delay.

If the first criterion K1 is not correct, four cases are distinguished and checked in a further criterion K2: K2a, K2b, K2c, K2d. For the case distinction, the accelerations a2 of the front vehicle 2 and the relative speed after the reaction time dv_t1 are used in each case.

The second criterion K2a is checked if a2 <0 and dv_t1 <0. Here, first of all, the equation of motion evaluation method BV1 is checked. If not, the second rating method BV2 is used.

If the second criterion K2a is satisfied, i. If the determined desired acceleration a1_d_1 or a_1_d2 exceeds a limit value, the necessity of an automatic deceleration of the own vehicle 1 results, since the driver will not be able to automatically set the necessary amount of deceleration after the end of his reaction time.

The third criterion K2b is checked if a2 <0 and dv_t1-i0. Here is always checked only with the help of the second evaluation BV2. This avoids the weakness of the equation of motion evaluation method BV1 in those situations where there is a strong deceleration of the front vehicle 2. If the third criterion K2b is satisfied, ie, the determined second setpoint acceleration a1_d_2 exceeds a limit value, the necessity of an automatic deceleration of the own vehicle 1 arises, since the driver does not respond after the end of his reaction time will be able to adjust the necessary amount of delay automatically.

The fourth criterion K2c is checked if a250 and dv_t1 <0. Here, it is always checked only with the aid of the equation of motion evaluation method BV1, since only evaluation method BV1 is relevant. The second evaluation method BV2 is not applicable here, since with a positive acceleration a2 of the front vehicle 2, no deceleration path s2_stop can be determined. The weakness of the motion equation evaluation method BV1 in situations characterized by a strong deceleration of the front vehicle 2 is not relevant in such situations, since only positive values for a2 are considered. If the fourth criterion K2c is satisfied, i. the determined first target acceleration a1_d_1 exceeds a limit, the need for an automatic braking of the own vehicle 1, since the driver will not be able to set the necessary amount of delay automatically after his reaction time.

The fifth criterion K2d is checked if a2> 0 and dv_t1 - 0. Here, the front vehicle 2 accelerates away from the own vehicle 1. This case is therefore safe overall, so that there is no need to initiate automatic emergency braking.

The statement "first, ... fifth criterion" expresses no order or significance.

Thus, according to the criteria K1, K2a to K2d, a control algorithm can be formed according to which the first criterion K1 is first checked and subsequently the case distinction is made in the criteria K2a, K2b, K2c and K2d, in which then the desired acceleration (as described). loading may delay) is determined as either a1_d_1 according to Equation 7 or as a1_d_2 according to Equation 14.

LIST OF REFERENCE NUMBERS

1 own vehicle

2 front object / vehicle

3 lane

4 distance sensor

5 driving dynamics system

6 control device

7 speed sensor

8 vehicle brakes

9 Warning indicator

Vertex of x1

Vertex of x2 x1 position of the first vehicle

x2 Position of the second vehicle

x1_0 Position of the first vehicle at time t = 0 x2_0 Position of the second vehicle at time t = 0 vi Speed of the first vehicle

v1_t1 Speed of the first vehicle after the reaction time t1 v2 Speed of the second vehicle

a1 Longitudinal acceleration of the first vehicle

a2 longitudinal acceleration of the second vehicle

a1_d_1 first target acceleration

a1_d_2 second target acceleration

dx relative distance

dx_min Minimum distance

dx_0 initial relative distance at time t = 0

dx_t1 Relative distance after the reaction time t1

dx 2 relative distance to BV 2 s1_br available braking distance of the first vehicle

s1_react Travel of the first vehicle traveled during t1 s2_stop Deceleration travel of the second vehicle to standstill dv Relative speed

dv_t1 Relative speed after the reaction time t1

M1 Relative distance measurement signal

M2 speed measurement signal

M3 brake control signals

Sil warning indication signal t time

t1 reaction time

t1_dv Self-deceleration time of the first vehicle (dv = 0, dx = dx_min) t2_stop Object deceleration time of the second vehicle / object until v2 = 0

BV1 evaluation procedure 1

BV2 evaluation procedure 2

BVO upstream assessment procedure

K1 first criterion

K2 further criterion

K2a second criterion

K2b third criterion

K2c fourth criterion

K2d fifth criterion

Zk1 Admissibility criterion

Claims

claims

1 . Method for determining an emergency braking situation of a first, own vehicle (1), in which the own vehicle (1) determines at least the following state variables:

its own driving speed (vi),

its own longitudinal acceleration (a1),

its relative distance (dx) to a front object (2), and a second speed (v2) and second acceleration (a2) of the front object (2),

wherein it is determined from the state variables (vi, a1, dx, v2, a2) by means of an evaluation method (BV1, BV2) whether an emergency braking situation exists,

characterized in that

depending on the state variables (vi, a1, dx, v2, a2), at least two different evaluation methods (BV1, BV2) are used to evaluate whether an emergency braking situation exists;

wherein it is determined as a function of the state variables (vi, a1, dx, v2, a2) which of the at least two different evaluation methods (BV1, BV2) is used.

2. A method for determining an emergency braking situation of a first, own vehicle (1) according to claim 1, characterized in that the different evaluation methods (BV1, BV2), at least the following assessment methods comprise:

an equation of motion evaluation method (BV1) in which a motion equation system of the own vehicle (1) and the front object (2) is determined, and

a braking distance evaluation method (BV2) in which a braking distance (s1_br) of the own vehicle (1) is determined.

3. Method according to one of the preceding claims, characterized in that it is determined on the basis of an admissibility criterion (Zk1) whether the first evaluation method (BV1) or the at least second evaluation method (BV2) is permissible and is used,

4. The method according to claim 3, characterized in that in the case that a self-braking time (t1_dv) that of the own vehicle (1) until reaching a minimum distance (dx_min) and the same speed (dv = 0) with the front object (2) is less than or equal to an object deceleration time (t2_stop), which requires the front object (2) to decelerate to a stop (v2 (t2_stop) = 0), the first evaluation method (BV1 ) and is used and, in the case that the self-deceleration time (t1_dv) is greater than the object deceleration time (t2_stop), the at least second evaluation method (BV2) is allowed and used.

5. The method according to any one of the preceding claims, characterized in that in the case of determining an emergency braking situation automatically initiated an emergency braking operation and / or a warning indication signal (Sil) is output.

6. Method according to one of the preceding claims, characterized in that in the determination of which of the evaluation methods (BV1, BV2) is to be used, and / or in individual evaluation methods additionally a reaction time (t1) of an in-vehicle brake system after the initiation of an automatic emergency braking and / or a response time (t1) of the driver after the issuance of the warning indication signal (Sil) via a warning display (9) is included.

7. The method according to claim 6, characterized in that in a first step in advance an upstream evaluation method (BVO) is used, in which it is evaluated whether a first criterion (K1) is satisfied, according to which the actual relative distance (dx) of the own vehicle (1) to the front object (2) after the reaction time (t1) is smaller than a minimum distance to be maintained ( dx_min),

wherein upon fulfillment of the first criterion (K1) an emergency braking situation is detected, and if the first criterion (K1) is not met, it is subsequently determined which of the further evaluation methods (BV1, BV2) is to be used.

8. The method according to claim 7, characterized in that when not fulfilling the first criterion (K1) below an assessment based on the second acceleration (a2) of the front object (2) and the relative speed after the reaction time (dv_t1) of the front object (2) to the own vehicle (1), wherein the relative speed (dv) after the reaction time (dv_t1) is formed as a difference of the second speed (v2) minus the own speed (vi).

9. The method according to claim 7 or 8, characterized in that when not meeting the first criterion (K1), the appropriate evaluation method (BV1, BV2) is determined as a function of further criteria (K2a, K2b, K2c, K2d), the other Criteria (K2a, K2b, K2c, K2d) include one or more of the following criteria:

a second criterion (K2a), which is fulfilled when the acceleration (a2) of the front object (2) is negative and the relative speed after the reaction time (dv_t1) is negative,

wherein upon fulfillment of the second criterion (K2a) an admissibility criterion (Zk1) is checked for the first evaluation method (BV1) and the first evaluation method (BV1) is carried out when the admissibility criterion (Zk1) is met, and if the admissibility criterion ( Zk1) the second evaluation method (BV2) is used, a third criterion (K2b), which is fulfilled when the second acceleration (a2) is negative and the relative speed after the response time (dv_t1) is greater than or equal to zero,

wherein the second evaluation method (BV2) is used when the third criterion (K2b) is fulfilled,

a fourth criterion (K2c) which is satisfied when the second acceleration (a2) is greater than or equal to zero and the relative speed after the response time (dv_t1) is negative, and when the fourth criterion (K2c) is met the first evaluation procedure (BV1) is used, and

a fifth criterion (K2d) which is satisfied if the second acceleration (a2) is greater than or equal to zero and the relative speed after the response time (dv_t1) is greater than or equal to zero,

and when the fifth criterion (K2d) is met, no determination of an emergency braking situation is carried out.

10. The method according to any one of the preceding claims, characterized in that with the evaluation method (BV1, BV2) in each case a desired acceleration (a1_d_1, a2_d_2) is determined.

11. The method according to any one of the preceding claims, characterized in that in the first evaluation method (BV1) the equations of motion of the own vehicle (1) and the front object (2) are placed in second order in time and have:

a current relative distance (dx), current acceleration values (a1, a2) of the own vehicle (1) and the front object (2) and current speeds (vi, v2) of the own vehicle (1) and the front object (2),

and it is determined whether the equations of motion stepping the minimum distance (dx_min) between the own vehicle (1) and the front object (2) yields.

12. The method of claim 10 or 1 1, characterized in that in the first evaluation method (BV1) a first target acceleration a1_d_1 is determined using the equation a1_d_1 = a2 ( ^dv - ^tl ) ² (Equation 7),

2 · (dx _ tl - dx _ min)

where a2 is the second acceleration, dv_t1 is the predicted relative speed after the reaction time (t1), dx_t1 is the predicted relative distance after the reaction time (t1) and dx_min is the minimum distance.

13. The method according to any one of the preceding claims, characterized in that in the second evaluation method (BV2) a second target acceleration (a1_d_2) is determined from a calculation which braking distance (s1_br) for the own vehicle (1) when initiating a braking after the reaction time (t1) remains based on the current values of the own speed (vi), second speed (v2) and second acceleration (a2), the current relative distance (dx) and the fixed minimum distance (dx_min).

14. The method according to claim 13, characterized in that the second target acceleration (a1_d_2) is determined based on the equation

al _{d 2} = ^vl - ' ^{1) 2} (Equation 14)

~ ~ 2 sl _br

with v1_t1 the own speed (vi) of the own vehicle (1) determined from the current own speed (vi) and actual own acceleration (a1) after the reaction time (t1) and the available braking distance (s1_br) of the own vehicle (1) Initiation of braking after the reaction time (t1).

15. Control device (6) for a vehicle dynamics control system (5) of a separate vehicle (1) for carrying out a method according to one of the preceding claims,

wherein the control means (6) for determining state variables (vi, a1, dx, v2, a2) receives:

a relative distance measurement signal (M1) of a distance sensor (4) for determining a relative distance (dx) to a preceding vehicle (2),

a speed measurement signal (2) from a speed sensor (7) for determining a separate speed (vi) of the own vehicle (1),

wherein the control device (6) furthermore determines or measures as state variables an own acceleration (a1) of the own vehicle (1), a second speed (v2) of the front object (2) and a second acceleration (a2) of the front object (2) and records internally or externally stored data for a reaction time (t1) and a minimum distance (dx_min) to be observed for the relative distance,

wherein the control device (6) determines from the state variables (vi, a1, dx, v2, a2) by means of an evaluation method (BV1, BV2) whether there is an emergency braking situation,

the control device (6), depending on the state variables (vi, a1, dx, v2, a2), using different evaluation methods (BV1, BV2) for assessing whether an emergency braking situation exists,

wherein the control device (6) determines in dependence on the state variables (vi, a1, dx, v2, a2) which of the plurality of evaluation methods (BV1, BV2) is to be used,

wherein the different evaluation methods (BV1, BV2) comprise at least the following evaluation methods:

an equation of motion evaluation method (BV1) for determining a motion equation system of the own vehicle (1) and of the front object (2), and

a braking distance evaluation method (BV2) for determining an available braking distance (s1_br) of the own vehicle (1),

wherein the control device (6) outputs braking control signals (M3) to vehicle brakes (8) and / or a warning indication signal (Sil) to the driver as a function of the determination.

16. vehicle dynamics control system (5) in particular brake control system or column driving system, in particular for carrying out a method according to one of claims 1 to 14,

wherein the vehicle dynamics control system (5) comprises a control device (6) according to claim 14, the distance sensor (4), the speed sensor (7) and the vehicle brakes (8).